1. Technical Field
The present invention relates to a semiconductor device.
2. Related Art
Conventionally, a structure of a power semiconductor element provided with a field stop layer has been known (please see Patent Document 1, for example). n-type impurities such as protons are implanted to the field stop layer.
Patent Document 1: Specification of U.S. Pat. No. 7,842,590
If n-type impurities such as protons are implanted to a semiconductor substrate, and the semiconductor substrate is subjected to thermal treatment, the impurities such as protons terminate defects and the like in the semiconductor substrate, and the carrier lifetime recovers. But if the carrier lifetime on the rear surface side of the semiconductor substrate becomes too long, tail current at the time of reverse recovery operation increases, and the reverse recovery loss increases.